A common toothbrush is designed such that bristles forming a brush are implanted at regular intervals on a head having the shape of a flat plate. In order to maximize the brushing effect by causing the brush to come into close contact with a curved surface of the teeth, a variety of methods are applied: different lengths may be assigned to the bristles to adjust the height thereof, large or small diameters may be provided to the bristles, or the bristles may be arranged in various patterns.